Method and apparatus for isolating and testing zones during reverse circulation drilling

ABSTRACT

A zone isolating and testing apparatus comprising an isolation tool and a downhole flow control means and a method of using such apparatus is disclosed. The zone isolating and testing apparatus is particularly useful for testing zones during reverse circulation drilling using concentric drill string such as concentric drill pipe or concentric coiled tubing. The isolation tool of the zone isolating and testing apparatus comprises an expandable packer means and is adapted to connect to concentric drill string near the drilling means. The downhole flow control means of the zone isolating and testing apparatus comprises two valves, one for closing off the annulus between the inner tube and outer tube of the concentric drill string and the other for closing off the inner space of the inner tube. The downhole flow control means is also adapted to connect to concentric drill string near the drilling means. During testing, the isolation tool seals off the annulus between the concentric drill string and the walls of the wellbore and the downhole flow control means seals off either the annulus between the inner tube and outer tube of the concentric drill string or the inner space of the inner tube of the concentric drill string.

This application claims the benefit of U.S. Provisional Application No.60/521,051, filed Feb. 11, 2004.

FIELD OF USE

The present invention relates to an apparatus and method for isolatingand testing individual zones in a vertical, directional or horizontalwellbore during drilling. More particularly, the present inventionrelates to a zone isolating and testing apparatus and method of usethereof to allow testing of isolated zones for flow of hydrocarbons,formation fluids and drill cuttings during vertical, horizontal ordirectional reverse circulation drilling of wellbores using concentricdrill pipe, concentric coiled tubing, or the like.

BACKGROUND OF THE INVENTION

The oil and gas industry uses various methods to test the productivityof wells prior to completing a well (see, for example, U.S. Pat. No.4,898,236). After drilling operations have been completed and a well hasbeen drilled to total depth or prior to reaching total depth in the caseof multi-zoned discoveries, it is common to test the zone to estimatefuture production of oil and gas. Current technologies used for testingreservoirs such as drill stem testing (DST) are often too expensive totest multi-zone reservoirs, particularly at shallow depths. Furthermore,isolating and testing zones using conventional packer technology can beslow, expensive and sometimes difficult to set and then release.

Traditionally the DST process involves flowing a well through a lengthof drill pipe reinserted through the static drilling fluid. The bottomof the pipe will attach to a tool or device with openings through whichfluid can enter. This perforated section is placed across an anticipatedproducing formation and sealed off with packers, frequently a pair ofpackers place above and below the formation. This packing off techniquepermits an operator to test only an isolated section or cumulativesection.

The present invention allows a fast, safe and economic way to isolateand test zones during reverse circulation drilling, alleviating the needto first remove the drill pipe used for drilling and then reinsert alength of drill pipe for testing.

SUMMARY OF THE INVENTION

A zone isolating and testing apparatus comprising an isolation tool anda downhole flow control means and a method of using such apparatus isdisclosed. The zone isolating and testing apparatus is particularlyuseful for testing zones during reverse circulation drilling usingconcentric drill string, e.g., concentric drill pipe, concentric coiledtubing and the like, said concentric drill string comprising an innertube and an outer tube forming an annulus therebetween. Thus, the zoneisolating and testing apparatus is preferably operably connected to aconcentric drill string.

The isolation tool of the zone isolating and testing apparatus comprisesan expandable packer means and is adapted to connect to concentric drillstring near the drilling means. When the packer means of the isolationtool is in the expanded position, the isolation tool is in the “closedposition” and when the packer means is in the contracted position theisolation tool is in the “open position”. In a preferred embodiment, theexpansion of the packer means is controlled by an electric current forquicker opening and closing of the isolation tool.

It is understood in the art that the area of the zone tested will bedictated by the distance the isolation tool is placed away from thedrilling means. In some instances where the bands of the pay zones areknown to be quite broad the isolation tool and the drilling means can beseparated from one another by several joints of concentric drill string.

The downhole flow control means of the zone isolating and testingapparatus comprises two valves, one for closing off the annulus betweenthe inner tube and outer tube of the concentric drill string and theother for closing off the inner space of the inner tube. The downholeflow control means is also adapted to connect to concentric drill stringnear the drilling means. In one embodiment, the isolation tool anddownhole flow control means are connected to each other. However, it isunderstood that these two components may be separated from one anotherby one or more joints of concentric drill string.

During the drilling process, the isolation tool is in the open position,i.e. the packer means is contracted. When the tool is in the openposition it does not significantly restrict the flow of hydrocarbons, asthe outside diameter of the isolation tool when in the open position ispreferably equal to or less than the outside diameter of the concentricdrill string. However, it is understood that the outside diameter of theopen isolation tool can also be greater than the outside diameter of theconcentric drill string and still not significantly restrict the flow ofhydrocarbons.

The downhole flow control means is also in the complete open positionduring drilling, i.e., both valves are open. This allows drilling fluidto be pumped down either the annulus or inner space of the concentricdrill string and exhaust drilling fluid and drill cuttings to be removedthrough the other of said annulus or inner space.

However, when testing is required during the reverse circulationdrilling process, the isolation tool is in the closed position, i.e. thepacker means expands to abut the adjacent wellbore walls. Further, oneof the two valves of the downhole flow control means is also in theclosed position. Which valve will be closed is dependent upon whetherdrilling fluid is being pumped through the annulus or the inner space.For example, if drilling fluid were being pumped down the annulus thenduring testing the annulus valve would be closed.

Thus, during testing, the zone of the wellbore below the isolation toolis shut off or isolated from the portion of the wellbore above the toolas the expanded packer means will not allow hydrocarbons to flow passedit. The materials present in the isolated zone can then flow througheither the annulus or inner space to the surface of the well fortesting.

The disclosed invention has one or more of the following advantages overconventional isolation packer technology and drill stem testing:

-   -   when drilling vertical, directional, and/or horizontal        wellbores, individual zones can be isolated and tested much        quicker and cheaper without having to interrupt drilling for        extended periods of time;    -   open hole testing provides very valuable production data;    -   zones which may otherwise be damaged by testing fluids when        using drill stem testing can now be tested without damage as        testing fluids are not necessary;    -   easier to measure the flow of formation fluids into a zone;    -   decisions on well stimulation can be made while the well is        being drilled; and    -   more accurate information on reservoir pressure, temperature,        flow rate etc. can be obtained from individual zones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of one embodiment of the isolation tool of thepresent invention.

FIGS. 2 a and 2 b is a schematic of the isolation tool in the open andclosed position, respectively.

FIG. 3 is a schematic of the downhole blow out preventor.

FIG. 4 is a schematic of the surface drilling and testing equipment usedin the present invention.

FIG. 5 is a schematic of the inner drill string of concentric drillstring of the present invention.

FIG. 6 is a schematic of one embodiment of the zone isolating andtesting apparatus typically used with concentric drill pipe.

FIG. 7 is a schematic of one embodiment of the zone isolating andtesting apparatus typically used with concentric coiled tubing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A zone isolating and testing apparatus comprising an isolation tool anda downhole flow control means and method of using such apparatus willnow be described with reference to the following preferred embodiment.

FIG. 1 schematically illustrates the isolation tool 30 of the zoneisolating and testing apparatus and means for attaching the isolationtool 30 between two pieces of concentric drill string 45 and 47.Concentric drill string 45 and 47 both comprise an inner tube 57 and anouter tube 59. Concentric drill string is designed such that at one endof concentric drill string is a threaded pin end and at the other end isa threaded box end. Thus, pieces of concentric drill string can beconnected end to end by screwing the threaded pin end of the new pieceof concentric drill string to be added into the box end of the drillstring below.

As can be seen in FIG. 1, concentric drill string 45 has threaded pinend 31 at its bottom end and concentric drill string 47 has threaded boxend 35 at its top end. Isolation tool 30 is adapted to be insertedbetween concentric drill string 45 and 47 by means of threaded box end37 and threaded pin end 33. Thus, threaded pin end 31 of concentricdrill string 45 screws into threaded box end 37 and threaded pin end 33screws into threaded box end 35 of concentric drill string 47.

Isolation tool 30 further comprises packer means 39. Packer means 39 canbe expanded or contracted by any means known in the art, for example, bymeans of an electric current flow path as shown in FIG. 5. In anotherembodiment, the packer means comprises an inflatable ring which can beinflated and deflated by pumping various types of fluid into and out ofthe ring.

FIGS. 2 a and 2 b schematically illustrate the isolation tool 30attached to the concentric drill string in the open and closed position,respectively. During drilling the isolation tool 30 is in the openposition and during testing it is in the closed position.

When packer means 39 is contracted or deflated as shown in FIG. 2 a, theisolation tool 30 is in the open position and hydrocarbons can flowfreely through the wellbore annulus 43 formed between the outer wall ofthe concentric drill string and the wellbore wall 41. When packer means39 is expanded or inflated as shown in FIG. 2 b, the packer means 39 isforced against wellbore wall 41 thereby closing annulus 43 tohydrocarbon movement above or below the packer means 39. Thus, thetesting region below the packer is isolated from the surface of thewellbore.

In order to test for hydrocarbon flow, formation fluids, drill cuttingsand the like present in the testing zone, the isolation tool is used inconjunction with a downhole flow control means or downhole blow outpreventor (downhole BOP) as shown in FIG. 3. In FIG. 3, downhole BOP 10is shown attached to the lower end of concentric drill string 47 bythreaded pin end 72 of concentric drill string 47 screwing into threadedbox end 70 of downhole BOP 10.

In this embodiment, downhole BOP 10 comprises two valve means 3 and 5for shutting off the flow of drilling fluid, exhausted drilling fluid,drill cuttings and/or hydrocarbons through one or the other of the outerannulus 7 formed between inner tube 57 and outer tube 59 of concentricdrill string 47 and inner space 9 of inner tube 57. It is understoodthat other downhole flow control means can also be used, for example,the downhole flow control means as described in U.S. Patent ApplicationsPublication Nos. 20030155156 and 20030173088, incorporated herein byreference.

Thus, in one embodiment of the invention, the isolation tool 30 and thedownhole BOP 10 of the zone isolating and testing apparatus can beseparated by a single joint of concentric drill string 47. However, itis understood that in some instances the isolation tool and downhole BOPcan be directly threaded or connected by other connection means to eachother. Further, it can be appreciated that the orientation of the twocomponents is not critical; in some instances it may be desirable tohave the downhole BOP attached to the bottom of the concentric drillstring first and the isolation tool connected either directly or bymeans of one or more joints of concentric drill string below thedownhole BOP.

It is understood that the drilling means (not shown) can be eitherdirectly attached to the bottom of the downhole flow control means, theisolation tool, other downhole tools or an intervening joint ofconcentric drill string. In general, however, the drilling means isattached to the last in the series of downhole tools.

During reverse circulation drilling with concentric drill string, bothvalves 3 and 5 of the downhole BOP 10 are in the open position (notshown). In one embodiment, drilling fluid is pumped from surfaceequipment through the annulus 7 formed between the inner tube 57 andouter tube 59 and exhausted drilling fluid, drill cuttings and/orhydrocarbons 19 flow through the inner space 9 to the surface of thewellbore. It is understood that drilling fluid could also be pumped fromsurface through the inner space 9 and exhausted drilling fluid, drillcuttings and/or hydrocarbons removed through the annulus 7.

When drilling is stopped for testing, the isolation tool 30, which islocated at or near the downhole BOP, is put in the closed position asshown in FIG. 2 b to isolate the testing region below the packer means.In the instance where drilling fluid is being pumped down the annulus 7and exhausted drilling fluid, drill cuttings and/or hydrocarbons flowthrough the inner space 9 to the surface of the wellbore, valve means 3of the downhole BOP 10 is also put in the closed position as shown inFIG. 3, as no fluids are being flowed from surface equipment duringtesting.

Valve means 5, however, remains in the open position as shown in FIG. 3thereby allowing hydrocarbons, formation fluids and/or drill cuttings(collectively referred to as reference 19 in FIG. 3) present in theisolated zone to flow to surface. Well flow test equipment known in theart will be able to determine the hydrocarbon content of the isolatedtesting area. Optionally, a surface blow out preventor (surface BOP, notshown) is provided to shut off the flow of hydrocarbon from the annulusbetween the drill string and the wellbore walls that may be present inthe zone above the packer means.

FIG. 4 schematically shows the surface equipment used during drillingand testing. Drilling rig 70 is equipped with well testing equipment 74.The hydrocarbons in the test region flow through the inner space of theinner tube of the concentric drill string and then through the chokemanifold system as shown in 72. Well flow test equipment can also belocated at the end of blewie line 78. Surface BOP 76 ensures that thereis no escape of hydrocarbons to the surface through the annulus formedbetween the drill string and the wellbore walls.

The isolation tool is preferably powered by an electric current forquicker opening and closing operations. FIG. 5 is a schematic of aportion of concentric drill string having threaded pin end 31 at oneend. The outer tube has been removed to reveal inner tube 57, which ispreferably made of a rubber type material, rubber/steel, fiberglass orcomposite material, capable of withstanding the forces and pressures ofthe drilling operations. Inner tube 57 further comprises electricalwires 51 that allow the flow of the electric current. Wire coils 53 and55 are compressed in each end of the concentric drill string when twopieces of concentric drill string are torqued (screwed) together. Thisprovides the electric current to operate the isolation tool, e.g., toexpand or contract the packer means as needed.

Other means of operating the isolation tool could include fiber opticcables, radio frequency and electric magnetic forces. When usingconcentric coiled tubing the isolation tool can be operated using smalldiameter capillary tubes which transmit hydraulic or pneumatic pressureto an actuator at or near the tool.

FIG. 6 shows one embodiment of the assembled zone isolating and testingapparatus of the present invention, which is typically used withconcentric drill pipe. In this embodiment, the isolation tool 30 and thedownhole BOP 10 are spatially separated by means of a single joint ofconcentric drill pipe 47. Typically, the drilling means (not shown) isattached either directly to the downhole BOP 10 or to other downholetools that can be attached to the downhole BOP. It may be desirable,however, particularly in instances where the bands of the pay zones areknown to be quite broad (i.e., 40 ft or greater), to have the isolationtool and the drilling means separated even further by additional jointsof concentric drill string.

FIG. 7 shows another embodiment of the assembled zone isolating andtesting apparatus, which is typically used when the concentric drillstring comprises a continuous length of concentric coiled tubing havinga continuous length of inner coiled tubing and a continuous length ofouter coiled tubing. In this embodiment, the isolation tool 30 isconnected to the bottom of the concentric coiled tubing 65 by connectionmeans known in the art. The downhole BOP 10 is then connected to theisolation tool 30 by similar connection means known in the art.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof. Various changes in the size, shapeand materials as well as the details of the illustrated construction maybe made without departing from the spirit of the invention.

1. An apparatus for isolating a zone in a hydrocarbon formation fortesting flow of hydrocarbons, formation fluids and/or drill cuttingsduring vertical, horizontal or directional reverse circulation drillingof a wellbore using concentric drill string, said concentric drillstring comprising an inner tube situated inside an outer tube andforming an annulus therebetween, comprising: (a) an isolation toolhaving an expandable and contractible packer means and adapted to beoperably connected to said concentric drill string; and (b) a downholeflow control means having a plurality of valve means for controlling theflow of hydrocarbons, formation fluids and drill cuttings through theannulus, the inner tube or both and adapted to be operably connected tosaid concentric drill string.
 2. The apparatus of claim 1 wherein saidconcentric drill string comprises joints of concentric drill pipe. 3.The apparatus of claim 1 wherein said concentric drill string comprisesconcentric coiled tubing.
 4. The apparatus of claim 1 wherein saiddownhole flow control means is operably connected to said concentricdrill string below said isolation tool.
 5. The apparatus of claim 1wherein said downhole flow control means is operably connected to saidconcentric drill string above said isolation tool.
 6. The apparatus ofclaim 2 wherein said isolation tool and said downhole flow control meansare separated from each other by one or more joints of concentric drillpipe.
 7. The apparatus of claim 1 wherein said inner tube is made of arubber material, rubber and steel, fiberglass or other compositematerial and comprises electrical wires and said packer means of saidisolation tool expands or contracts by means of an electric currentdelivered by the electrical wires of the inner tube.
 8. The apparatus ofclaim 1 wherein said packer means comprises an inflatable ring.
 9. Theapparatus of claim 8 wherein said inflatable ring expands or contractsby pumping fluids into or out of the inflatable ring.
 10. The apparatusof claim 1 wherein said isolation tool and said downhole flow controlmeans are further adapted to be connected to each other.
 11. A methodfor isolating a zone in a hydrocarbon formation for testing flow ofhydrocarbons, formation fluids and/or drill cuttings during vertical,horizontal or directional reverse circulation drilling of a wellboreusing concentric drill string, said concentric drill string comprisingan inner tube situated inside an outer tube and forming an annulustherebetween, comprising: (a) sealing off an outside annulus formedbetween a wall of said wellbore and an outer surface of said concentricdrill string to form an isolated testing zone; (b) sealing off one ofsaid annulus between the outer tube and the inner tube of the concentricdrill string or said inner space of the inner tube of the concentricdrill string; (c) allowing hydrocarbons, formation fluids and/or drillcuttings present in said isolated testing zone to flow through the otherof said annulus between the outer tube and the inner tube of theconcentric drill string or said inner space of the inner tube of theconcentric drill string to the surface of said wellbore; and (d)measuring the amount of hydrocarbons, formation fluids and/or drillcuttings present in said isolated testing zone.
 12. The method of claim11 wherein the outside annulus is sealed off by means of an isolationtool comprising an expandable and contractible packer means.
 13. Themethod of claim 12 wherein said packer means is expanded and contractedby means of an electrical current.
 14. The method of claim 12 whereinsaid packer means is expanded and contracted by means of addition offluid into or removal of fluid from the packer means.
 15. The method ofclaim 11 wherein the annulus between the outer tube and the inner tubeof the concentric drill string or the inner space of the inner tube ofthe concentric drill string is sealed off by means of a downhole flowcontrol means comprising a plurality of valve means.
 16. The method ofclaim 111 wherein said concentric drill string comprises joints ofconcentric drill pipe.
 17. The method of claim 11 wherein saidconcentric drill string comprises concentric coiled tubing.